1. Field of the Invention
The present invention relates to a method of growing a single crystal, and more particularly to a method of growing a high quality single crystal from a melt by controlling the temperature distribution of the melt.
2. Description of the Related Art
Conventionally, there has been controlled the temperature distribution of the solid crystal in order to obtain a high quality single crystal, which enables to increase the yield rate of electronic devices such as semiconductor. This is to control the stress induced by the contraction resulting from cooling after crystallization, or the behavior of the point defects generated during cooling.
Briefly introducing such conventional art for controlling the temperature distribution of the solid crystal in order to obtain a high quality single crystal, Korean Patent Application No. 2000-0013028 discloses a means for controlling the temperature distribution of a GaAs single crystal grown to resolve the thermal stresses formed therein, and Japanese Patent Application No. Pyoung-2-119891 discloses hot zones employed to reduce lattice defects of a silicon single crystal during the cooling process. Further, Japanese Patent Application No. Pyoung-7-158458 discloses a means for controlling both the temperature distribution and the pulling rate of a single crystal being grown, and Japanese Patent Application No. Pyoung-7-66074 discloses a method of resolving the defect density of a single crystal by improving the hot zones and controlling the cooling rate. Korean Patent Application No. 1999-7009309 (USSN. 60/041,845) also discloses a means for restraining the formation of the defects by changing the hot zones and controlling the cooling rate. In addition, Korean Patent Application No. 2002-0021524 has proposed an improvement in the thermal shield and water-cooled tubes to increase the yield rate of high quality single crystals.
However, such conventional technologies are based on reactions in the solid phase, thus suffering the following problems. First, although Korean Patent Application No. 1999-7009309 (USSN. 60/041,845) is intended to reduce the supersaturated point defects leading to the crystal defects by means of diffusion process, it is impossible to be applied for practical applications because the processing time taken for maintaining the temperature at a proper level is too long, i.e., about 16 hours or more.
Second, the invention based on the theory of the reactions in the solid phase cannot provide for large-scale production. For example, although Korean Patent Application No. 2001-7006403 has proposed an improvement in the thermal shield and water-cooled tubes, the pulling rate is only 0.4 mm/min that is too low to yield high quality single crystals at high productivity.
There has been proposed another conventional technology for achieving a high quality single crystal, which is to control the solid-liquid interface (crystal growing interface). For example, Japanese Patent Application No. Pyoung-4-173474 and Korean Patent Application No. 1993-0001240 describes a method of controlling the solid-liquid interface for obtaining a compound single crystal of high quality such as GaAs, and Korean Patent Application No. 1998-026790 and U.S. Pat. No. 6,458,204 defines the form of the solid-liquid interface to achieve a silicon single crystal of high quality. Nevertheless, even according to Korean Patent Application No. 1999-7009309 involving such form of solid-liquid interface, it is impossible to obtain a high quality single crystal. Thus, such conventional technologies cannot sufficiently provide for the productivity of high quality single crystals.